Electronic equipment, such as a mobile communication device or a mobile computing device, is subject to various electronic tests after production. Such tests are generally necessary to ensure proper configuration, calibration and functionality of various elements of the devices under test (DUT). For testing purposes, specific testing devices are employed which simulate a testing environment under predefined testing conditions. For example, testing devices may employ one or more specific testing routines with predefined testing schedules. Those testing schedules regularly involve input of particular test signal sequences into the DUT and/or reception of responses to testing signals input to the DUT. Such responses may be evaluated for consistency, constancy, timeliness and other properties of an expected behaviour of the DUT.
Of particular relevance are tests and testing devices for electronic equipment which is operated in an environment sensitive to radio frequency (RF) signals. Such equipment may be used to output, receive, measure or otherwise process RF-sensitive parameters and signals. Those tests are conventionally performed using standardized testing routines conducted by specifically designed testing equipment that is connected to a DUT.
Network analyzers are commonly used instruments designed to measure network parameters of electrical networks. Due to the ease of measurement of reflection and transmission at high frequencies network analyzers commonly measure s-parameters, but other network parameter sets such as y-parameters, z-parameters, and h-parameters may be measured as well. Network analyzers are often used to characterize two-port networks such as amplifiers and filters, but they can be used on networks with an arbitrary number of ports.
Network analyzers require periodic calibration. Typically such calibration is performed once per year, for example by a manufacturer or by a third party in a calibration laboratory. The accuracy and reliability of a network analyzer may be enhanced if systematic errors in the instrument are corrected and the characteristics of cables, adapters and test fixtures are accounted for. Additionally, user calibration may be performed in order to correct for any errors during operation of the network analyzer.
Network analyzers have connectors on its front panel to which test cables may be connected. The length of those cables will inter alia introduce time delays, corresponding phase shifts, and attenuation, all of which may affect the outcome of measurements done by the network analyzer. Calibration usually involves measuring known standards and using those measurements to compensate for systematic errors. Calibration may be a time-consuming and cumbersome task for both the engineer using the network analyzer as well as the manufacturer during periodic calibration.
Document U.S. Pat. No. 6,823,276 B2 discloses systems and methods for flexible and accurate test apparatus error value calculation. Document U.S. Pat. No. 7,019,536 B1 discloses methods for calibrating a multi-port vector network analyzer.